In conventional network systems, especially when playing games, it is often the case that, a server is previously set as a master device for controlling communications. A network configured in such a manner ceases to function if the master device is disconnected therefrom, so that a game player is forced to stop game play. Also, wireless communication network systems are widely used because of their well-known high degree of connection/disconnection flexibility. Note that the “disconnection of a device from a network” as described herein occurs, for example, when power of the device has been suddenly shut down, when the device has moved to a location where no radio waves from the network reach the device, when the device has logged off of the network, when any error has occurred with the device, when the device has frozen, and so on.
In the technology disclosed by Japanese Patent No. 2867980, one candidate wireless communication terminal device for use in constructing a network acts as a temporary master, and collects data concerning the latest received field intensity at the time from other candidate wireless communication terminal devices for use in constructing the network. Then, another terminal device is assigned as the temporary master to collect data concerning the latest received field intensity at the time from other candidate wireless communication terminal devices for use in constructing the network. Thereafter, based on the results of the collection, a candidate for a master device is selected from among all the candidate wireless communication terminal devices for use in constructing the network such that the received field intensity is satisfactory to all the terminal devices.
In the technology disclosed by Japanese Patent No. 2924828, one candidate wireless communication terminal device for use in constructing a network acts as a temporary master, and collects information concerning the amount of remaining power and data transfer rate from other candidate wireless communication terminal devices for use in constructing the network. Based on the results of collection, the temporary master determines, as a master device, a candidate wireless communication terminal device whose transfer rate is the highest among other candidate wireless communication terminal devices and whose remaining power is equal to or more than a predetermined value.
In the technology disclosed by Japanese Patent No. 3421017, if a network is constructed by a master device (network master) and a plurality of slave devices, the order of priority for assigning the role of a backup master to the slave devices is determined, and information concerning the priority order is shared between all the slave devices. If the master device (network master) is disconnected from the network, each terminal device having acted as a slave device sequentially attempts to connect to terminal devices, which have a higher priority as a backup master in descending order of priority among the terminal devices, so as to connect to a network in which the first device to which the terminal device is successfully connected acts as a network master. Alternatively, if the terminal device recognizes that there is no terminal device having a higher priority as a backup master within the range where communication is possible, then the terminal device behaves as a network master and waits for a connection request from a terminal device having a lower priority as a backup master.
According to the first reference, however, in order to determine a master device, it is required that a plurality of wireless communication terminal devices sequentially act as a temporary master for collecting data from all other terminal devices, and therefore time in accordance with the number of terminal devices is required for constructing a network.
Also, it is conceivable that, in a network game system based on the premise that, for example, game players with hand-held game devices having a radio communication function gather and play games together within such a range that they can see each other's faces, the received field intensity of each hand-held game device is satisfactory even if any hand-held game device acts as a master device. Accordingly, an excessive processing load is caused by collecting information concerning the received field intensity in a manner as disclosed in the first reference.
Also, it is conceivable that in a network game system, which is supposed to be comprised of a plurality of hand-held games of the same type, for example, the hand-held game devices are substantially identical in data transfer rate. Accordingly, an excessive processing load is caused by collecting information concerning the data transfer rate in a manner as disclosed in the second reference.
Further, neither of the first two references disclose how to deal with a situation where the master device is disconnected from a network in midstream.
In the technology disclosed in the third reference, when the master device is disconnected from a network, a slave device is set as a new master device based only on a predetermined order of priority. Accordingly, the degree of freedom in selecting a slave device as a candidate for a master device is low. Also, no description is given about a process to be performed when a master device is disconnected from a network constituted by two devices, i.e., the master device and a slave device.
Therefore, a feature of an exemplary illustrative embodiment is to provide a wireless network system where, when a plurality of terminal devices having a radio communication function are started, master and slave devices are automatically selected from among the terminal devices without causing users to set the master and slave devices.
Another feature of an exemplary illustrative embodiment is to provide a network system which allows master and slave devices to be set through a relatively simple and lightweight process.
Still another feature of an exemplary illustrative embodiment is to provide a network system with a high degree of freedom in selecting a new master device for use in constructing a new network when a previous master device has been disconnected.
Still another feature of an exemplary illustrative embodiment is to provide a network system which allows a master device to be determined more reliably to reconstruct a network.
Still another feature of an exemplary illustrative embodiment is to provide a network system which allows a network to be reconstructed with slave devices which had previously comprised the network together with a master device, the master device having been disconnected from the network.
Still another feature of an exemplary illustrative embodiment is to provide a network system which allows a slave device to connect to a master device in another network if a network to which the slave device has previously belonged cannot be reconstructed with any other slave device previously belonging to the same network.
The exemplary illustrative embodiments have the following aspects to attain the features mentioned above. The reference numerals or the like indicated between parentheses are merely provided to help in understanding the present invention in light of the exemplary illustrative embodiments to be described later, and are not to be taken as limiting.
A first aspect of an exemplary illustrative embodiment is directed to a wireless network system comprising a plurality of terminal device's (10) having a radio communication function, one of the plurality of terminal devices acting as a master device for controlling data transfer timing in a network, each terminal device other than the master device acting as a slave device performing data transfer with the master device under control of the master device.
Each of the plurality of terminal devices includes: a master device search section (21, 43); a temporary master process section (21, 44); a switching section (21, 45); a slave process section (21, 42); and a master process section (21, 41). The master device search section is operable to search for any other terminal device acting as the master device or a temporary master device. The temporary master process section is operable to cause the terminal device itself to act as the temporary master device. The switching section is operable to, if no network is constructed with any other terminal device, perform a switching operation for alternately activating the master device search section and the temporary master process section (see FIG. 4). The slave process section is operable to, if the master device search section detects the presence of the master device or temporary master device, cause the terminal device itself to act as a slave device for the detected master device or temporary master device. The master process section is operable to, if another terminal device is detected as searching for the master device or temporary master device during a period for which the terminal device itself is caused by the temporary master process section to act as the temporary master device, cause the terminal device itself to act as the master device.
Herein, the situation “where no network is constructed with any other terminal device” includes a situation immediately after the terminal device has been turned on and a situation immediately after a network has ceased to exist because a master device was disconnected from the network in which the terminal device belonged.
In a second aspect of an exemplary illustrative embodiment, based on the first aspect, the switching section performs the switching operation for alternately activating the master device search section and the temporary master process section, and the switching section randomly sets one or both of a period in which to activate the master device search section and a period in which to activate the temporary master process section.
In a third aspect of the an exemplary illustrative embodiment, based on the first aspect, each of the plurality of terminal devices transmits, at regular intervals, a beacon signal including at least information, which indicates that the terminal device itself is acting as the master device or temporary master device when acting as the master device or temporary master device respectively, and the master device search section receives a beacon signal transmitted from any other terminal device to detect the presence of the master device or temporary master device.
In a fourth aspect of the an exemplary illustrative embodiment, based on the first aspect, each of the plurality of terminal devices further includes a master device disconnection determination section (21, 47) for, when the terminal device itself is acting as the slave device, determining whether the master device is disconnected from a network in which the terminal device itself belongs, and if the master device disconnection determination section detects that the master device is disconnected from the network, the switching section automatically starts the switching operation.
Note that any known method can be employed for determining whether the master device is disconnected from the network. For example, it may be determined that the master device is disconnected from the network when a beacon signal transmitted from the master device has ceased to be received, or it may be determined that the master device is disconnected from the network when the slave device side has received a signal transmitted from the master device when disconnected from the network indicating the same.
In a fifth aspect of the an exemplary illustrative embodiment, based on the fourth aspect, each of the plurality of terminal devices further includes an identification information storage section (21, 48) for, when a network is constructed with any other terminal device, receiving and storing identification information for identifying that another terminal device is in the network, and the master device search section searches for any other terminal device, which is acting as the master device or temporary master device and has previously belonged in the network, based on the identification information stored in the identification information storage section.
In a sixth aspect of the an exemplary illustrative embodiment, based on the fifth aspect, after a predetermined period of time has elapsed since the master device disconnection determination section determined that the master device is disconnected from the network, the master device search section searches for, in addition to terminal devices having previously belonged in the network, a terminal device acting as the master device or temporary master device.
In a seventh aspect of an exemplary illustrative embodiment, based on the fifth aspect, the identification information is a MAC address list which lists a MAC address of any other terminal device having previously belonged in the network.
In an eighth aspect of an exemplary illustrative embodiment, based on the seventh aspect, each of the plurality of terminal devices transmits, at regular intervals, a beacon signal including at least its own MAC signal when acting as the master device or temporary master device, and when the presence of any other terminal device acting as the master device or temporary master device has been detected, the master device search section checks a MAC address of that other terminal device, which is included in the beacon signal transmitted from that other terminal device, with the MAC address list stored in the identification information storage section, and determines whether that other terminal device has previously belonged in the network in which the terminal device has previously belonged.
In a ninth aspect of an exemplary illustrative embodiment, based on the fourth aspect, each of the plurality of terminal devices further includes an individual number storage section (21, 48) for, when a network is constructed with any other terminal device, receiving and storing a list of an individual number of that other terminal device in the network, and when the master device disconnection determination section has determined that the master device is disconnected from the network, the switching section compares the individual number list stored in the individual number list with an individual number of the terminal device, and sets, based on a comparison result, an initial period in which to activate the master device search section.
In a tenth aspect of an exemplary illustrative embodiment, based on the ninth aspect, the individual number is a MAC address of a terminal device.
According to the first aspect, when constructing a completely new network or reconstructing a network having ceased to exist because a master device is disconnected therefrom, it is arbitrary as to which terminal device acts as a master device or a slave device. Thus, as compared to a case where a specific terminal device is always caused to act as a master device, it is possible to construct a wireless network comprised of one master device and one or more slave devices in a more flexible manner.
According to the second aspect, it is randomly determined which terminal device acts as a master device and which terminal device acts as a slave device. Thus, it is possible to prevent the processing load due to the operation as the master device from being concentrated on a specific terminal device.
According to the third aspect, by using a beacon signal generally used in a wireless network system, it is possible to detect the presence of the master device or temporary master device.
According to the fourth aspect, even if a network has ceased to exist because a master device is disconnected therefrom, the network can be automatically reconstructed.
According to the fifth aspect, even if a network has ceased to exist because a master device is disconnected therefrom, the network can be reconstructed by slave devices having previously belonged in the network.
According to the sixth aspect, when a network has ceased to exist because a master device is disconnected therefrom, even if it is not possible to reconstruct the network by slave devices having previously belonged in the network, it is possible to construct a new network with another terminal device located with the range where communication is possible. Thus, for example, even if a master device is disconnected from a network comprised of the master device and one slave device, a new network can be automatically constructed by the remaining slave device and any terminal device located within the range where communication is possible.
According to the seventh aspect, it is ensured that each terminal device can be identified by a MAC address.
According to the eighth aspect, by using a beacon signal generally used in a wireless network system, a terminal device can readily determine whether any other terminal device having transmitted the beacon signal has previously belonged in the same network as the terminal device.
According to the ninth aspect, when a master device is disconnected from a network, a period in which to start acting as a temporary master varies from one remaining slave device to another in accordance with their individual numbers. Thus, it is possible to prevent a plurality of slave devices from simultaneously starting to act as the temporary master.
According to the tenth aspect, when a master device is disconnected from a network, a period in which to start acting as a temporary master is determined based on a MAC address. Thus, it is ensured that the period in which to start acting as a temporary master varies from one remaining slave device to another.